KR100253054B1 - Aligner and exposure method using the same - Google Patents

Abstract

The present invention is characterized in that it is possible to prevent the deterioration of the depth of focus in the optical exposure apparatus of the scanning exposure method.

For example, the reticle position measuring device 71 measures the vertical position of the reticle 30 in accordance with the movement in the scan direction of the reticle stage 31 before the actual scan exposure. The offset correction data is obtained by the calculation circuit 72 together with the measured value and stored in the memory 72a. Thereafter, data in the memory 72a is sequentially supplied to the feedback control circuit 62 at the time of actual scan exposure. As a result, the wafer Z-axis driving mechanism 54 is controlled in accordance with the position in the Z-axis direction of the wafer 50 and the position in the up-down direction of the reticle 30, and the reticle 30 is changed by the change in the height position of the reticle 30. ) Is configured to correct the deviation of the picked-up image from the focal coincidence position on the exposure surface 50a on the wafer 50.

Description

Exposure apparatus and exposure method

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an exposure apparatus and exposure method for exposing a photoresist on a wafer surface by, for example, a pattern formed on a reticle. In particular, the present invention relates to a scan exposure type optical exposure apparatus that performs exposure while relatively moving a reticle and a wafer. Will be.

In general, in a lithography process in semiconductor manufacturing, a reduction projection type optical exposure apparatus (optical stepper) has been used for a long time. Currently, it is possible to form the minimum line width of devices at the quarter micron level.

Therefore, the resolution (RES) of the line micron level line width in the optical stepper can be achieved by high NA of the projection lens and short wavelength of the exposure light wavelength [lambda], as shown in Equation (1) below.

RES = k1 * λ / NA --- (1)

DOF = k2 * λ / (NA) ² --- (2)

Here, k1 and k2 are both integers, and NA is the numerical aperture of the projection lens.

However, as shown by equation (2), high NA of the projection lens and short wavelength of the exposure light wavelength cause a decrease in the depth of focus (DOF) of the projection lens so that the pattern image of the reticle becomes blurry on the exposure surface of the wafer. There was a problem that it is easy to cause a sea fault.

In order to solve this problem, it is required to accurately match the projection image from the reticle with the exposure surface of the wafer.

Fig. 9 shows a schematic configuration of a conventional light stepper to improve the reduction in DOF.

That is, this light stepper irradiates the reticle 3 with the light from the light source 1 via the condenser lens 2, for example, and the pattern image formed in the reticle 3 is irradiated by the projection lens 4 with the wafer ( 5) The surface of the surface of the wafer 5 is exposed by reduction projection, and the position of the exposed surface of the wafer 5 at that time is measured by the wafer position measuring device 6, whereby the optical axis (Z axis) of the wafer 5 is measured. It is comprised so that the projection image from the reticle 3 and the exposure surface of the wafer 5 may be matched with high precision by adjusting the position of a direction.

The wafer position measuring device 6 is composed of, for example, an LED 6a and a light receiver 6b (PSD), and the drive system in the Z axis direction of the wafer 5 so that the output of the light receiver 6b is always "0". (Not shown) was to control.

However, in the above-described wafer position measuring device 6, only information regarding the height position of the exposure surface of the wafer 5 is obtained, that is, at the height position of the pattern surface of the reticle 3 which is one of the causes of the DOF decrease. The flaw was that no information could be obtained.

That is, the conventional optical stepper fixes the reticle 3 on the stage 3 '(reticle stage), and changes the position of the stage 5' (wafer stage) on which the wafer 5 is mounted in this state to expose the reticle 3. Since the so-called step-and-repeat method was adopted, the warpage (curvature or inclination) and the vertical motion of the reticle 3 were regarded as negligible, and information on the height position of the pattern surface of the reticle 3 was not necessary.

Recently, however, a so-called scan exposure type photoexposure apparatus has been developed which enables the reduction of the diameter of the projection lens and the like to perform exposure by relatively moving the reticle and the wafer.

In the optical exposure apparatus of this kind, the warp and the vertical movement of the reticle during the scanning exposure cause a decrease in the DOF.

For example, when the warp and the vertical movement of the reticle pattern surface in the optical axis direction are ΔZm, the change ΔZm of the focus position on the exposure surface of the wafer is expressed by the following expression (3).

ΔZw = ΔZm * R ² --- (3)

Where R is the reduction ratio of the projection lens.

That is, in the case of a scan exposure type optical exposure apparatus having a reduction ratio R of the projection lens of 1/4 when the amount ΔZm of warp of the reticle is 2 μm, the change ΔZw of the focus position on the exposure surface of the wafer is about 0.13. It becomes micrometer and cannot be ignored.

As described above, in the conventional optical exposure apparatus of a scanning exposure method in which exposure is performed by relatively moving a reticle and a wafer, the cause of the DOF deterioration due to the warping or the vertical movement of the pattern surface of the reticle during the scanning exposure. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above point, and an object thereof is to provide an exposure apparatus and an exposure method which can prevent a decrease in depth of focus due to a change in height position of a pattern surface of a reticle during scanning exposure.

1 is a configuration diagram showing an outline of a reduced projection type optical exposure apparatus of an ehls scan exposure method in accordance with one embodiment of the present invention.

2 is a schematic cross-sectional view showing the principal part of the construction of the optical exposure apparatus of the scanning exposure method.

3 is similarly shown for explaining the measurement operation of the reticle position measuring device in the case where warpage exists in the reticle.

4 is similarly shown for explaining the measuring operation of the reticle position measuring device when the reticle moves up and down.

5 is a schematic view showing a configuration example of a reticle position measuring device according to another embodiment of the present invention.

6 is a schematic diagram showing the case where the reticle position measuring device is similarly constructed using a laser interferometer.

7 is a schematic view showing another example of the configuration of the reticle position measuring device.

8 is similarly shown for explaining another configuration of the reticle position measuring device.

9 is a schematic configuration diagram of an optical stepper shown in order to explain the prior art and its problems.

<Explanation of symbols for main parts of drawing>

11 light source 11a exposure light beam

11b: illumination region 21: condenser lens

30: reticle 30: pattern surface

30b: glass surface 31: reticle stage

32: Reticle X axis drive mechanism 33: Reticle Y axis drive mechanism

34: Reticle Z axis drive mechanism 41: projection lens

50: wafer 50a: exposed surface

51: wafer stage 52: wafer X axis drive mechanism

53: wafer Y axis drive mechanism 54: wafer Z axis drive mechanism

61: wafer position measuring device 61a: LED

61b: PSD 62: feedback control circuit

71, 100, 200: Reticle position measuring device

71a: LED 71b: PSD

72: arithmetic circuit 72a: memory

81: main controller 101: laser interferometer

102: power mirror 103: receiver

104: laser light 201a, 202a: LED

201b, 202b: PSD

An exposure apparatus according to the present invention for achieving the above object is an optical system for projecting the pattern image formed on the reticle on the wafer, the reticle is mounted, the reticle stage movable in a direction perpendicular to the optical axis direction of the optical system, A wafer stage on which the wafer is mounted and movable in a direction perpendicular to the optical axis direction of the optical system and the optical axis direction of the optical system, and the reticle surface of the reticle surface based on movement in a direction perpendicular to the optical axis direction of the optical system. Reticle surface position measuring means for measuring the position in the optical axis direction of the optical system, and when projecting the pattern image of the reticle by the optical system on the wafer based on the measured value of the reticle surface position measuring means of the optical system of the wafer. And adjusting means for adjusting the position in the optical axis direction.

In the exposure method of the present invention, in the case of scanning the pattern image formed on the reticle while moving the reticle and the wafer and projecting the pattern image on the wafer, the wafer surface is exposed by the pattern image of the reticle. The height position in the direction orthogonal to the scan direction of the reticle surface is measured in accordance with the movement in the scan direction, and the height position in the direction orthogonal to the scan direction of the wafer is adjusted based on the measured value.

According to the exposure apparatus and the exposure method of the present invention, the change in the depth of focus of the projection image from the reticle on the exposure surface of the wafer can be corrected according to the warp and the vertical movement of the reticle. This makes it possible to perform scan exposure in a state where the projection image from the reticle and the exposure surface of the wafer are always in focus.

EXAMPLE

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

Fig. 1 shows a schematic structure of a reduced exposure type optical exposure apparatus of a scanning exposure method according to one embodiment of the present invention.

That is, the exposure light beam 11a from the light source 11 is irradiated in the slit image to the reticle 30 (mask) as a projection light plate by the condenser lens 21. Then, the projection image from the reticle 30 in the illumination region 11b is projected on the wafer 50 in the slit image via the projection lens 41 (optical system).

At this time, the reticle 30 and the wafer 50 are relatively moved so that the entire pattern image formed on the surface on the projection lens 41 side of the reticle 30, that is, on the pattern surface 30a, becomes the projection lens ( 41 is reduced to a predetermined magnification and projected onto the exposure surface 50a on the wafer 50.

A photoresist is applied to the exposure surface 50a on the wafer 50, and the resist is exposed by the reduced pattern image photographed through the projection lens 41.

As the light source 11, a mercury lamp which emits light, for example, g-line or i-line light, which is effective for photosensing the photoresist applied to the exposure surface 50a of the wafer 50 is used.

The reticle 30 is in the X-axis direction and Y-axis direction perpendicular to the optical axis direction (the optical axis direction of the projection lens 41) of the light beam 11a, and in the Z-axis direction parallel to the optical axis direction of the light beam 11a, respectively. It is mounted on the movable reticle stage 31. Movement of the reticle stage 31 in the X-axis direction, that is, movement in the scan direction is performed by the reticle X-axis driving mechanism 32, and movement in the Y-axis direction is performed by the reticle Y-axis driving mechanism 33, in the Z-axis direction. Are moved by the reticle Z-axis drive mechanism 34, respectively.

The wafer 50 is mounted on the wafer stage 51 which is movable in the X-axis direction and Y-axis direction perpendicular to the optical axis direction of the luminous flux 11a and in the Z-axis direction parallel to the optical axis direction of the luminous flux 11a, respectively. do. Movement of the wafer stage 51 in the X-axis direction, that is, movement in the scan direction is performed by the wafer X-axis driving mechanism 52, and movement in the Y-axis direction is performed by the wafer Y-axis driving mechanism 53, in the Z-axis direction. Is moved by the wafer Z-axis driving mechanism 54, respectively.

Further, in this optical exposure apparatus, a wafer position measuring device 61 for precisely matching the projection image from the reticle 30 with the exposure surface 50a on the wafer 50 is provided. The wafer position measuring device 61 receives, for example, an LED 61a for irradiating light to the exposure surface 50a of the wafer 50 and the reflected light to a height position of the exposure surface 50a of the wafer 5. It is comprised by the PSD 61b which measures related information, ie, the position of the optical axis 11 (Z-axis direction) of the light beam 11a.

The PSD 61b electrically detects the difference between the light-receiving position of the reflected light at the time of focus matching, for example, according to the position in the Z-axis direction of the wafer 50. The output of this PSD 61b is supplied to the feedback control circuit 62.

The feedback control circuit 62 controls the wafer Z-axis driving mechanism 54 to correct the output of the PSD 61b of the wafer position measuring device 61, that is, the difference at the time of focal matching, and thus the wafer 50. To adjust the position in the Z-axis direction.

The optical exposure apparatus is also provided with a reticle position measuring device 71 to accurately match the projection image from the reticle 30 with the exposure surface 50a on the wafer 50 with high accuracy. The reticle position measuring device 71 receives, for example, the LED 71a for irradiating light onto the pattern surface 30a of the reticle 30 and the reflected light, and moves in the scan direction of the reticle stage 31. PSD which measures the position of the height position of the pattern surface 30a of 30, ie, the curvature (curvature and inclination) of the reticle 30, or the up-down movement (the optical axis direction (Z-axis direction) of the light beam 11a). It consists of 71b.

The PSD 71b electrically detects the position in the Z-axis direction of the reticle 30 by the difference in the light-receiving position of the reflected light. The output of this PSD 71b is supplied to the arithmetic circuit 72.

The calculation circuit 72 calculates a correction value for adjusting the position of the wafer 50 in the Z-axis direction according to the position of the Z-axis direction of the reticle 30 based on the output of the PSD 71b.

The correction value of the calculation circuit 72 is supplied to the feedback control circuit 6 that controls the wafer Z axis drive mechanism 54 as offset data.

Here, in one embodiment of the present invention, for example, a memory 72a (memory unit) for storing correction values is prepared in the calculation circuit 72, and the correction values stored before the scan exposure are read out in the case of scan exposure. It is configured to supply to the feedback control circuit 62.

That is, the reticle stage 31 is moved in the scanning direction before actually starting the exposure to scanning, and at that time, the reticle position measuring device 71 measures the change in the position of the reticle 30 in the Z axis direction. The correction value is calculated by the calculation circuit 72 based on the measured value, and is stored in the memory 72a as offset data.

Thereafter, the data in the memory 72a is sequentially supplied to the feedback control circuit 62 based on the movement in the scan direction of the reticle stage 31 during the actual scan exposure. In this way, the feedback control circuit 62 is not only the position in the Z axis direction of the wafer 50 by the wafer position measuring device 61 but also the position in the Z axis direction of the wafer 50 and the Z axis of the reticle 30. The wafer Z axis drive mechanism 54 is controlled in accordance with the position in the direction.

As a result, in the case of movement of the wafer 50 in the scanning direction due to the scanning exposure, the position in the Z-axis direction of the wafer 50 causes the projection image from the reticle 30 and the exposure surface 50a on the wafer 50 to be moved. The movement of the wafer stage 51 is adjusted so that the position of the reticle 30 is offset by the change in the Z-axis direction and the change position at the focal point matching (differential).

In addition, in the optical exposure apparatus having the above-described configuration, its operation (each part) is controlled by the main control part 81.

For example, the main control unit 81 emits light from the light source 11, drives the respective drive mechanisms 32, 33, and 34 to move the reticle stage 31 in the X, Y, and Z directions, and the wafer stage 51. Driving of the driving mechanisms 52 and 53 for moving in the X and Y directions, emitting light from the LED 61a of the wafer position measuring device 61, emitting light from the LED 71a of the reticle position measuring device 71, and the like. To control.

The drive mechanisms 32, 33, 34 for moving the reticle stage 31 and the drive mechanisms 52, 53, 54 for moving the wafer stage 51 are, for example, motors or piezoelectric elements. It consists of a well-known structure which consists of these.

Fig. 2 is a cross-sectional view showing the main part of the configuration of the optical exposure apparatus of the scanning exposure method.

That is, the wafer position measuring device 61 is provided in the space portion between the projection lens 41 and the wafer stage 51, for example, the LED 61a and the PSD 61b are arranged in accordance with the scanning direction. The light emitted from the LED 61a and reflected from the exposure surface 50a of the wafer 50 is sequentially received by the PSD 61b as the wafer 50 moves in the scanning direction.

On the other hand, in the reticle position measuring device 71, LEDs 71a and PSD 71b are arranged in the space portion between the projection lens 41 and the reticle stage 31 according to the scanning direction. As the reticle 30 moves in the scanning direction, the light emitted from the LED 71a and reflected by the pattern surface 30a of the reticle 30 is sequentially received by the PSD 71b.

3 shows a measurement operation of the reticle position measuring device 71 when warpage exists in the reticle 30.

For example, when warpage exists in the reticle 30, the reticle 30 when warpage does not exist in the optical path 91 of light reflected from the pattern surface 30a of the reticle 30 and incident on the PSD 71b. Compared to the optical path 92 of the light reflected from the pattern surface 30a of the light incident on the PSD 71b, the optical path difference 93 is generated according to the amount of warpage.

By detecting this optical path difference 93 electrically by the PSD 71b, the amount ΔZm of the warpage of the reticle 30 can be measured.

The amount DELTA Zm of this deflection is obtained as a function DELTA Zm (x, y) of the position of the reticle 30 in the x and y directions (the direction perpendicular to the optical axis direction of the light beam 11a).

Therefore, in the case of scan exposure, the wafer Z-axis driving mechanism 54 is offset by the amount corresponding to the function ΔZm (x, y) to correct the position in the wafer Z-axis direction according to the curvature of the reticle 30. This can reduce the deterioration of the depth of focus (DOF) due to the change in the position of the reticle 30 in the Z-axis direction.

4 shows the measurement operation of the reticle position measuring device 71 when the reticle 30 moves up and down in the case of movement in the scan direction.

For example, when the reticle 30 moves up and down, the optical path 94 of light that is reflected from the pattern surface 30a of the reticle 30 and enters the PSD 71b does not have the up and down movement of the reticle 30. Compared to the optical path 95 of the light reflected from the pattern surface 30a and incident on the PSD 71b, the optical path difference 96 occurs due to the vertical motion.

By detecting this optical path difference 96 electrically by the PSD 71b, the vertical movement ΔZm of the reticle 30 can be measured.

The vertical movement ΔZm is obtained as a function ΔZm (x, y) of the position of the reticle 30 in the x and y directions.

Therefore, in the case of the scanning optical path, the wafer Z-axis driving mechanism 54 is offset by the amount corresponding to the function ΔZm (x, y), so that the position in the Z-axis direction of the wafer 50 is set in the reticle 30. This can be corrected according to the vertical movement, thereby reducing the deterioration of the depth of focus (DOF) due to the change in the position of the reticle 30 in the Z-axis direction.

According to the scanning exposure type reduction projection optical exposure apparatus having such a configuration, it is possible to obtain information regarding the height position of the pattern surface 30a of the reticle 30 during the scanning exposure. For this reason, the fall of DOF can be improved by correcting the height position of the wafer 50 according to the change of the height position of the pattern surface 30a of the reticle 30.

As described above, the deviation of the focal coincidence position on the projection from the reticle on the exposure surface of the wafer can be corrected in accordance with the warp and the vertical movement of the reticle surface.

That is, not only the information regarding the height position of the exposure surface of the wafer but also the information regarding the height position of the pattern surface of the reticle during scanning exposure can be obtained. As a result, scanning exposure can be performed while the projection image from the reticle and the exposure surface of the wafer are always in focus. Therefore, it is possible to prevent a decrease in the depth of focus due to the warping of the reticle and the vertical movement of the reticle during the scanning exposure.

In addition, in one embodiment of the present invention described above, the case in which the position of the wafer in the Z axis direction is adjusted in accordance with the warp and the vertical movement of the reticle has been described. However, the present invention is not limited thereto. It is also possible to correct the misalignment of the focal coincidence position of the projection image from the reticle on the exposure surface of the wafer by adjusting the position of the wafer, thereby preventing the deterioration of the depth of focus due to the warp and the vertical movement of the reticle during scanning exposure. can do.

In addition, not only the wafer or the reticle, but also the reticle and the wafer, for example, can also be realized by adjusting the position of the three-character Z-axis including the projection lens in a range where the magnification of the projection image does not change. have.

Further, the correction value obtained by calculation based on the measured value of the height position of the reticle obtained by preliminarily scanning exposure is stored in the memory 72a as offset data in advance, and the actual scan exposure is used by using the data. Although the deviation of the focal coincidence position in the projection from the reticle on the exposure surface of the wafer is corrected in the city, the correction value obtained by calculation is calculated based on the measured value of the height position of the reticle obtained at the actual scanning exposure, for example. In this case, the misalignment of the focal coincidence of the projection image from the reticle on the exposure surface of the wafer may be corrected in real time without using the memory.

The reticle position measuring device 71 is not limited to the case where the height position is measured by the pattern surface 30a of the reticle 30. For example, as shown in FIG. 5, the height position of the reticle 30 is measured. By the glass surface 30b, the LED 71a and the PSD 71b may be arranged to be arranged on the upper portion of the reticle 30.

The reticle position measuring device can also be configured using a mechanical sensor or the like.

For example, as shown in FIG. 6, the reticle position measuring apparatus 100 is comprised by the laser interferometer 101, the half mirror 102, the light receiver 103, etc., and the laser is located in the state which avoided the position of the wafer 50. FIG. The laser beam 104 from the interferometer 101 is reflected by the half mirror 102 and irradiated to the reticle 30 through the projection lens 41 to move the reticle 30 in the scan direction. The light reflected from the light 30a may be configured to be received by the light receiver 103 via the projection lens 41 and the half mirror 102.

In this case, since the warpage and the vertical motion of the reticle 30 can be measured through the projection lens 41, defects of the projection lens 41 such as distortion can be corrected at the same time.

In any case, the reticle position measuring device is not limited to measuring one point of the reticle 30. For example, as shown in Fig. 7, the reticle is composed of two sets of LEDs 201a and 202a and PSDs 201b and 202b. The position measuring device 200 may be configured to measure the height position at two points P1 and P2 of the pattern surface 30a of the reticle 30.

Further, for example, when the four points P1, P2, P3, and P4 of the pattern surface 30a of the reticle 30 are measured as shown in FIG. 8, in addition to the warp and the vertical movement of the reticle 30 in the diagonal direction. It is also possible to measure the slope of.

In addition, various modifications can be made without departing from the spirit of the invention.

On the other hand, the reference numerals written along the components of the claims of the present application to facilitate the understanding of the present invention, not intended to limit the technical scope of the present invention to the embodiments shown in the drawings.

As described above, according to the present invention, it is possible to provide an exposure apparatus and an exposure method capable of preventing a decrease in depth of focus due to a change in the height position of the pattern surface of the reticle during scanning exposure.

Claims (5)

Optical systems 11, 21, 41 for projecting the pattern image formed on the reticle 30 onto the wafer 50, and the reticle stage 31 on which the reticle is mounted and movable in a direction perpendicular to the optical axis direction of the optical system. And a wafer stage 51 on which the wafer is mounted and movable in a direction perpendicular to the optical axis direction of the optical system and the optical axis direction of the optical system, based on movement of the reticle stage in a direction perpendicular to the optical axis direction of the optical system. A reticle surface position measuring means (71) for measuring a position in the optical axis direction of the optical system of the reticle surface, and projecting the pattern image of the reticle by the optical system on the wafer based on the measured value of the reticle position measuring apparatus. The exposure apparatus comprising adjustment means (54, 62, 72, 72a) for adjusting the position in the optical axis direction of the optical system of the wafer. Wafer surface position measuring means 61 for measuring the position in the optical axis direction of the optical system on the wafer surface in accordance with the movement in the direction perpendicular to the optical axis direction of the optical system, and the wafer surface position measuring means in accordance with the measured value of the wafer surface position measuring means. And control means (54, 62) for controlling the position in the optical axis direction of the optical system, wherein the adjusting means gives a correction value to the control means based on the measured value of the reticle position measuring device as an offset. An exposure apparatus characterized by the above-mentioned. An exposure method of scanning a pattern image formed on the reticle while moving a reticle and a wafer and projecting the pattern image on the wafer, wherein the wafer surface is exposed by the pattern image of the reticle. And measuring the height position in the direction orthogonal to the scan direction of the reticle surface, and adjusting the height position in the direction orthogonal to the scan direction of the wafer based on the measured value. The adjustment value of the height position of the direction orthogonal to the scanning direction of the said wafer is a correction value computed from the measured value of the height position of the direction orthogonal to the scanning direction of the said reticle according to the movement to the scanning direction of the said reticle. Is stored in advance and is performed according to the correction value. The adjustment value of the height position of the direction orthogonal to the scanning direction of the said wafer is a correction value computed from the measured value of the height position of the direction orthogonal to the scanning direction of the said reticle according to the movement to the scanning direction of the said reticle. Exposure method characterized in that carried out according to. The adjustment value of the height position of the direction orthogonal to the scanning direction of the said wafer is a correction value computed from the measured value of the height position of the direction orthogonal to the scanning direction of the said reticle according to the movement to the scanning direction of the said reticle. Is given as an offset for correcting the height position of the wafer.